Of air-conditioning systems, air-conditioning systems are present which are made up of an air-conditioning apparatus which includes an indoor unit and an outdoor unit, and a controller which collects operation information on the air-conditioning apparatus from the air-conditioning apparatus through communication. In some cases, the controller is capable of controlling the plural air-conditioning apparatuses. Such a controller is connected to the plural air-conditioning apparatuses such that it can communicate therewith, and collects operation information on each of the air-conditioning apparatuses from each air-conditioning apparatus.
In a computer room or a similar space, a large number of servers are installed. In order to remove heat generated from those servers, and keep the temperature of the room at a constant level, the above air-conditioning system including the plural air-conditioning apparatuses is provided in the computer room. In order to keep the temperature of the computer room at a constant level, the controller controls the operations of the plural air-conditioning apparatuses.
If a further server or servers is added to the computer room, an air-conditioning apparatus or apparatuses are also added in accordance with the number of added servers. In the case where the computer room has been operated for many years, there is a case where an air-conditioning apparatus having been operated for ten and several years and a latest air-conditioning apparatus coexist in the room. Because of a technical progress of air-conditioning apparatuses, in general, the latest model of air-conditioning apparatuses have a higher coefficient of performance (COP) than those of old models of air-conditioning apparatuses. In the case where an air-conditioning system including air-conditioning apparatuses having different COPs performs control to keep the temperature of a computer room at a constant level, an air-conditioning apparatus having a lower COP consumes a larger amount of power than an air-conditioning apparatus having a higher COP, though the loads on the air-conditioning apparatuses are equivalent to each other.
Patent literature 1 discloses an example of an air-conditioning system including plural outdoor units having different COPs. To be more specific, patent literature 1 discloses the following technique: with respect to three outdoor units, an operation-capability distribution table for determining priorities for operating them based on the COP characteristics, maximum COPs and capacities of them is prepared in advance, and in accordance with a required load, based on the operation-capability distribution table, the load is distributed to two outdoor units having higher priorities, and the operation of the remaining outdoor unit is made in a stopped state. In such a manner, an outdoor unit or units having a higher priority are started, to thereby achieve a high efficient operation.